1. Field of the Invention
The present invention relates to a semiconductor device used, for example, for motor control on electric railway equipment or motor vehicle equipment.
2. Background Art
Japanese Patent Laid-Open No. 2006-66595 discloses a multilayer substrate in which a plurality of metal plates are joined together, with ceramic substrates interposed therebetween. In this multilayer substrate, a through hole in each ceramic substrate is filled with a metal to connect the metal plates on the upper and lower surfaces of the ceramic substrate to each other.
Filling the through hole in each ceramic substrate enables the metal plate (inter-ceramic metal) interposed between each adjacent pair of ceramic substrates to be used as an electrode. However, there is a problem that stress is concentrated on the periphery of the through hole in each ceramic substrate by thermal expansion or the like of the metal plates and a crack is thereby caused in the ceramic substrate. Also, breakage of the ceramic substrate can occur as a result of the growth of the crack.